The level of hardness in water can have a deleterious effect in many cleaning systems. For example, when hard water alone, or in conjunction with cleaning compositions, contacts a surface, it can cause precipitation of hard water scale on the contacted surface. Water can contain magnesium and calcium which can cause scale deposit and other metal ions such as iron, manganese and copper which produce stains that are very difficult to remove. In general, hard water refers to water having a total level of calcium and magnesium ions in excess of about 100 ppm expressed in units of ppm calcium carbonate. Although most locations have hard water, water hardness tends to vary from one location to another.
Chelating agents and/or threshold agents are often used in cleaners because of their ability to solubilize and/or prevent calcium and magnesium salts from precipitating. When calcium and magnesium salts precipitate, the crystals may attach to the surface being cleaned and cause undesirable effects in a variety of cleaning systems. For example, calcium carbonate precipitation on the surface of ware can negatively impact the aesthetic appearance of the ware, giving an unclean look. In a region with high levels of metal ions in water, staining can be a significant issue.
It is known to use acidic compositions to clean hard surfaces and that such formulations show good overall cleaning performance and good limescale removal and prevention. Indeed, for example WO 2004/018599 describes acidic hard surface cleaning compositions comprising an acid or a mixture thereof.
However, there are limitations to the convenience of acidic compositions employed as surface cleaners. It is known that some hard surfaces, such as enamel and several metals, e.g. aluminum, are sensitive to acids and may be severely damaged by acidic compositions used to clean said surfaces.
The type of acid used has also presented problems in development of acid cleaners. Most acid cleaners are based upon phosphoric acid due to its low cost, good combining ability with other ingredients, its ability to exert a very strong synergistic cleaning affect, and its low corrosivity, however, phosphoric acid has recently fallen out of favor due to environmental concerns.
Liquid compositions are also less economical as they have increased transportation costs. Solid products are generally more convenient, safe and economical also because they do not spill or splash, have reduced manufacturing and distribution costs, and require less storage space. However, solid products must first be converted to a liquid before they can be used in most applications. Typically, a product dispenser is used to bring water into contact with a solid product in order to dissolve the solid product and produce a resulting liquid “use” solution that can be transferred to a vessel or onto a surface to be cleaned.
It is therefore one object of this invention to provide a phosphate free acid composition which has excellent scale removal performance without the use of phosphoric acid.
It another object of the present invention to provide an acidic composition that can be manufactured in solid form and that is easily dissolved into a use solution.
It is another object of the present invention to provide an acidic surface treating/acidic destaining composition that provides good limescale removal performance whilst showing a good surface safety profile on the treated surface.
In particular, it is an objective of the present invention to provide a liquid or solid composition which may be used in combination with a variety of hard surface cleaners that provides an acceptable limescale stain removal.
It is yet another object of the present invention to provide an acidic composition in combination with reducing agents to decolorize and remove metal containing stains.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the appended claims.